Sedimentation apparatus

ABSTRACT

The invention relates to sedimentation apparatus (1) for treating liquid containing solids, such as sewage, whereby solid constituents of the liquid are substantially removed for subsequent handling/treatment and the liquid now clean of solids is taken off separately for subsequent treatment. To the end, the apparatus (1) comprises two lamella separators (2) the flow channels (3) of which are at an angle to the direction of flow &#34;S&#34; of liquid containing solids towards the inlet (4) to the separators. In the embodiment the angle is substantially 90°.

The invention relates to sedimentation apparatus, particularly to suchapparatus including a lamella separator.

It will be understood that the expression lamella separator used hereinrefers to a pack, set, cassette or the like of spaced plates ofundulating configuration, adjacent plates being joined at the crests ofthe undulations to provide channels through which a liquid can flow, theflow being generally laminar. Such separators are usually arranged sothat the channels are inclined to the vertical, and a liquid usuallycontaining solids in suspension is passed through channels from thelower end to the upper end (as considered in use) so that solidsseparate from the liquid and fall back under gravity down the channelsto the lower end of the lamella separator, which lower end thus alsoprovides an outlet for separated solids as well as an inlet for liquidcontaining solids. The upper end of the separator then forms an outletfor liquid from which solids have been substantially removed by passagethrough the separator.

There may be more than one separator in a sedimentation apparatus andthe or each separator may be removed bodily from the apparatus.

U.S. Pat. No. 2,973,866 and EP-A-0245140 relate to lamella separatorswhich generally seek to act on sewage, but do not provide an efficientmeans for separating solid contents thereof.

According to a first aspect of the invention there is providedsedimentation apparatus for separating solids from a liquid containingsame, characterised by at least one lamella separator the flow channelsof which are at an angle to the direction of flow `S` of liquidcontaining solids towards the inlet to the separator, characterised bydistribution means comprising a channel for receiving incoming liquidcontaining solids and directing it downwardly through the apparatus tothe inlet to the separator, by means for passing liquid containingsolids to one end of the channel, and by inlet means along the channeladapted for passing said liquid from the channel towards the inlet tothe separator.

The angle may be at substantially 90° to said flow direction. Thisprovides for extension of the apparatus in a modular fashion,longitudinally and/or laterally.

There may be two sets of lamella separators in the apparatus, thechannel being substantially centrally situated therebetween. Thisprovides for an efficient construction and operation.

There may be five spaced nozzles in a base of the channel. This providesfor optimum distribution.

There may be means to maintain grease, fat and the like suspended in theliquid in the channel. This assists in prevention of clogging,particularly where the means may comprise a gas distribution meansextending along the channel.

The distribution means may comprise a pipe in the channel with spacedair outlets. This is a relatively simple distribution means.

The pipe may be along one side of the channel, or alternatively, theremay be two pipes, which may extend along both sides of the channel.Either construction provides for efficient flotation.

There may be means to remove scum from liquid in the channel. Thisassists in maintaining the separator clean.

The scum removal means may comprise a weir, suitably a normallysubmerged weir at an end of the channel opposite an inlet for theliquid. This provides for a *shearing of scum from the liquid surface.

The weir may lead to a scum receiver having a normally closed valvemeans which may be openable to lower the level of scum and/or liquid inthe receiver, whereby the weir acts to remove the scum.

There may be separated solids receiver means of the apparatus, suitablycomprising a plurality of hoppers at one end of the apparatus and meansto direct the solids to the hoppers.

The means to direct the solids may comprise a scraper device. Thisprovides for relatively efficient sludge removal.

The scraper device may comprise a frame with transverse scraper bladesand means for reciprocating the scraper device.

The scraper device may be operated intermittently. This isenergy-conserving.

There may be means for cleaning the or each lamella separator,preferably comprising means for passing a cleaning fluid towards asolids outlet of the or each separator. This acts as a sponge device forcleaning.

The means may comprise a system of distributors below the or eachlamella separator. This is a construction which is economical of space.

The distributors may comprise diffuser pipes extending transversely ofthe apparatus below the or each separator, and the system may bereciprocably mounted below the or each separator.

Suitably the system may be mounted on the scraper device. This providesa compact yet efficient arrangement.

The diffuser pipes may be substantially parallel and set atapproximately the pitch of the blades of the scraper device. Thisprovides for cleaning of substantially the whole of the under surfacearea of a separator. The cleaning fluid may be air, or alternativelywater.

Sedimentation apparatus embodying the invention is hereinafterdescribed, by way of example with reference to the accompanyingdrawings.

FIG. 1 is a plan view of sedimentation apparatus including lamellaseparators according to the invention;

FIG. 2 is a side elevational view of the apparatus of FIG. 1;

FIG. 3 is an end elevational view of the apparatus taken on arrow `A` inFIG. 1;

FIG. 4 is an enlarged view of a central channel of the apparatus ofFIGS. 1 to 3;

FIG. 5 is a side view of part of distribution means of the apparatus ofFIGS. 1 to 3;

FIG. 6 is an enlarged view of a distribution nozzle of the distributionmeans of FIG. 5;

FIG. 7 is a schematic perspective view of a lamella separator platecleaning system according to the invention;

FIG. 8 is an enlarged exploded view of a riser of the system of FIG. 7;and

FIG. 9 is a detailed view of the laminar plate cleaning system of FIG.7.

Referring to the drawings, there is shown sedimentation apparatus 1 fortreating liquid containing solids, such as sewage, whereby solidconstituents of the liquid are substantially removed for subsequenthandling/treatment and the liquid now clean of solids is taken offseparately for subsequent treatment.

To the end, the apparatus 1 comprises two lamella separators 2 the flowchannels 3 of which are at an angle to the direction of flow `S` ofliquid containing solids towards the inlet 4 to the separators. In theembodiment the angle is substantially 90°.

In the embodiment too, the sedimentation apparatus 1 is substantiallyrectangular in plan and is open topped, and has a catwalk or walk-way 5at an upper level adjacent the open top, the walk-way being gained by astair 6.

There are two banks of lamella separators 2 along each side 7, 8 of theapparatus 1, the plates of the separators being indicated at `X` in FIG.1, the bottom (as viewed) or inlet of the separators being at the level`Y` (FIG. 2) and the liquid outlet from the separators being at the top,`Z`.

The lower part of the part of the apparatus 1, below the separators 2,is a receptacle 9 in which solids in the form of sewage sludge iscollected when that sludge, separated from the liquid in the lamellaseparators 2, passes out of the lower outlet end of those separators.The sludge is periodically removed to sludge collecting means in theform of two conical hoppers 10 at one end 11 of the apparatus 1. Removalis effected by a reciprocable scraper device 12 comprising a framehaving in the embodiment three longitudinally extending andsubstantially parallel bars or shoes 13 each of which sits on alongitudinally extending pad of plastic 14 on the base of the apparatusand which provides for relatively friction free reciprocation. The barsor shoes 13 carry transverse scraper blades 15 of wedge shape so thatthe inclined face of the wedge pushes sludge towards and into thehoppers 10 for subsequent handling. The device 12 includes areciprocable piston and cylinder arrangement 16, usually hydraulic, foroperation.

Access to the sludge receptacle 9 is gained through a door 17, in a sidewall of the apparatus 1, there being a platform 18 reached by a stair19, adjacent the door 17 so that an operative can stand on the platformto gain access to the door.

Extending longitudinally of the apparatus 1 between the banks of lamellaseparators 2 is a channel 20. This channel 20 is a distributor means forincoming liquid to be treated, and is situated at the top of theapparatus 1.

The channel 20 is thus at or adjacent the upper ends of the lamellaseparators 2, which upper ends provide the outlet for liquid from whichsolids have been separated after passage through the lamella separators2 from the bottom, the inlet thereto. Sewage to be treated passes up ariser stilling chamber 21 at one end of the channel and flows into thechannel 20 over plate 22. The sewage then passes down distribution meansin the form of five spaced tubes 23 with conical inlets 20' to chambersholding the lamella separators 2 which are flooded upwardly, asdescribed previously, for separation of sewage as sludge, which thenpasses to the receptacle 9 for ultimate removal to the hoppers 10. Thechannels of the separators are inclined in the general direction of thelongitudinal axis of the apparatus 1. The liquid to be treated, as itcomes from a central channel, passes laterally to the separatorchannels, that is the axis of the channels in the separators are atright angles to the flow direction to the separators 2. This arrangementprovides for flexibility in that the apparatus 1 can be scaled up bothlongitudinally and/or laterally as desired by adding on as many lamellaseparators as desired. The apparatus 1 is therefore modular.

In the channel 20 is flotation means in the form of an air pipe 24 alongeach side of the channel 20, the pipes 24 each having spaced air outletsfor passing air into the liquid in the channel 20. This air contactslight solid fractions such as grease and fats and floats theseconstituents whilst keeping other solids suspended. The fats or greasestherefore mostly do not pass to the separators 2, which could be blockedthereby, and are removed in a manner to be described. In an alternativethere is an air distributor or diffuser pipe 24 along only one side ofthe channel 20. Air passing into the liquid, in the channel 20 at thisone side effectively reduces the density of the liquid at that side.This promotes a circular or spiral flow in the liquid as the denser asthe denser liquid at the other side displaces the lighter liquid. Ascouring action is thus set up which keeps the solids suspended, whilstfloating the grease and fat to the surface.

At the end of the channel opposite the riser entry or stilling chamber21 for the liquid to be treated there is a normally submerged weir 25forming an entry to a sump 26. The channel 20 has a flat bottom butbecause of the liquid flow being from one end, the tendency is for theliquid to flow to the end adjacent the weir 25. In doing so, lightmatter such as scum and floated grease and fat collects at the end ofthe channel 20 adjacent the weir 25. When sufficient scum has been builtup over the weir 25 to merit removal, a normally closed valve (notshown) at the bottom of the sump 26 is opened, the liquid level drops,and the scum is effectively creamed or "chopped off" by the weir 25 andfalls into the sump 26 for disposal to drain. Alternatively the scumcould be passed to the hoppers 10, the valve is closed, and fresh scumis collected as it is pushed by the incoming liquid flow to the weir endof the channel 20.

The incoming liquid can be fed to the channel by any desirable meansproviding it ultimately enters the channel at the end opposite the weir25.

Although fat and grease is floated off the liquid, some is passed to thelamella separators 2 the channels 3 of which can become clogged withplugs of fat and grease, or even other material such as rag, at thebottom of the channels. To seek to overcome this, the apparatus 1includes a plate cleaning system 27 which in the embodiment is a frameof air distribution pipes 28 which is mounted on the scraper frame 12and thus reciprocates bodily with that scraper frame. The airdistribution pipes 28 effectively provide an air sponge system.

The pipes 28 are transverse, like the scraper blades 15, and are mountedon risers 29. There are flexible air lines 31 feeding the pipes 28 withair from an air manifold. The air diffuses out through air holes 32 inthe pipes 28, above the level of the sludge. There is a transverse pipeat every scraper blade, in other words the adjacent pipes 28 are set atthe pitch of the scraper blades 15. Thus, as the scraper device 12reciprocates, the whole of the underside surface area of the separators22 is covered. The air can be introduced continuously or intermittentlyand, in rising up, air bubbles from the diffusers dislodge any plugs inthe separator channels. An alternative plate cleaning system utiliseswater, issuing as streams, jets or bursts from the pipes 28. In thiscase, the water level in the sludge receptacle would be lowered to belowthe level of the pipes by suitable valving, before the water issues forcleaning the plates.

In either embodiment, cleaning can take place intermittently, whendesludging, which could be on a weekly bases, or as desired.

The body of the apparatus 1 is usually fabricated from metal plates (theseparators could be and usually are plastic plates), but the apparatuscould be built in situ from concrete, and the channel could be concrete.

I claim:
 1. Sedimentation apparatus for separating solids from a liquidcontaining same, comprising at least one lamella separator includingflow channels and an inlet thereto, the flow channels being disposed atan angle to the direction of flow `S` of liquid containing solidstowards the inlet to the separator, distribution means including areceiving channel for receiving incoming liquid containing solids anddirecting it downwardly through the apparatus to the inlet to theseparator said receiving channel further including means to maintaingrease, fat, and the like suspended in the liquid in the channel meansfor passing liquid containing solids to one end of the receivingchannel, and inlet means along the receiving channel for passing saidliquid from the receiving channel towards the inlet to the separator. 2.The apparatus of claim 1, wherein the angle is substantially 90° to saidflow direction `S`.
 3. The apparatus of claim 2, wherein there are twosets of lamella separators in the apparatus, and wherein the receivingchannel is substantially centrally situated therebetween.
 4. Theapparatus of claim 1, wherein said inlet means includes five spacedinlets in a base of the receiving channel.
 5. The apparatus of claim 1,wherein the means to maintain grease, fat and the like suspended in theliquid in the receiving channel comprises a gas distribution deviceextending along the channel.
 6. The apparatus of claim 5, wherein thedistribution device comprises a pipe in the receiving channel withspaced air outlets.
 7. The apparatus of claim 7, wherein the pipe isalong one side of the receiving channel.
 8. The apparatus of claim 6,wherein there are two pipes, extending along both sides of the receivingchannel.
 9. The apparatus of claim 1, further comprising means to removescum from liquid in the receiving channel.
 10. The apparatus of claim 9,wherein the means to remove scum comprises a weir at an end of thereceiving channel opposite an inlet for the liquid.
 11. The apparatus ofclaim 10, wherein the weir is a normally submerged weir.
 12. Theapparatus of claim 11 wherein the weir leads to a scum receiving havinga normally closed valve means which is openable to lower the level ofscum and/or liquid in the receiver.
 13. The apparatus of claim 1,wherein said apparatus further comprises a separated-solids receivermeans.
 14. The apparatus of claim 13, wherein said separated-solidsreceiver means comprises a plurality of hoppers at one end of theapparatus and by means to direct the solids to the hoppers.
 15. Theapparatus of claim 14, wherein the means to direct the solids comprisesa scraper device.
 16. The apparatus of claim 15, wherein the scraperdevice comprises a frame with transverse scraper blades and means forreciprocating the scraper device.
 17. The apparatus of claim 16, whereinthe scraper device is operated intermittently.
 18. The apparatus ofclaim 15, wherein there is a system of distributors mounted on thescraper device.
 19. The apparatus of claim 18, wherein the distributorscomprises pipes that are substantially parallel and set at approximatelythe pitch of the blades of the scraper device.
 20. The apparatus ofclaim 1, further comprising means for cleaning said at least one lamellaseparator.
 21. The apparatus of claim 20, wherein the cleaning meanscomprises means for passing a cleaning fluid towards a solids outlet ofsaid at least one separator.
 22. The of claim 21, wherein the means forpassing a cleaning fluid comprises a system of distributors below saidat least one separator.
 23. The apparatus of claim 22, wherein thedistributors comprise pipes extending in a transverse direction in theapparatus below said at least one separator.
 24. The apparatus of claim22, wherein the cleaning means is reciprocably mounted below said atleast one separator.
 25. The apparatus of claim 21, wherein the cleaningfluid is air.
 26. The apparatus of claim 21, wherein the cleaning fluidis water.